High hydraulic pressure forging device

ABSTRACT

A high hydraulic pressure forging apparatus wherein the accelerative operation of a hammer means in a cylinder causes said hammer means to strike a liquid received within a liquid chamber, to in turn provide operating force to a plunger in operative engagement with the liquid for the displacement of a movable die mounted on the plunger in opposition to a fixed die.

limited States Patent 'lominagai 1 Mar. 2%, 1972 [541 HIGH HYDRAULIC PRESSURE 1,106,741 8/1914 Slick ..72/402 FQRGING DEVHQE 3,205,790 9/1965 Bollar.... ....72/453 3,277,691 10/1966 Beche.... ....72/453 [72] Inventor: l-llroslii Tomlnaga, Kanagawa-ken, Japan 29 5 1/1967 nun/453 3,332,273 7/1967 Beche.... ....72/453 [73] Ass'gnee gg gzfis 2: Kalmshm Misha 3,352,143 11/1967 Bollar ....72/453 g P 3,370,450 2/1968 Scheucher ....72/453 [22] Filed: Jan. 21, 1969 3,451,249 6/1969 Sharon ..72/402 [21] APPL 794,473 Primary Examiner-Charles W.Tanham Assistant Examiner-Gene P. Crosby [30] Foreign Application Priority Data Attorney-Blum, Moscov1tz,Fr1edman & Kaplan Jan. 30, 1968 Japan I. ..43/5543 [57] I ABSTRACT Jan. 31 1968 Japan ..43/5597 A high hydrauhc pressure forgmg apparatus wherein the ac- Mar. 15, 1968 Japan ..43/17020 celerative operation ofa hammer means in a cylinder Causes said hammer means to strike a liquid received within a liquid [52] chamber, to in turn provide operating force to a plunger in 1 1 B213 7/ 28 operative engagement with the liquid for the displacement of a [58] Field of Search ..72/402, 453, 399 bl di t d on the plunger in opposition to a fixed die. [56] References Cited 6 Claims, 12 Drawing Figures UNITED STATES PATENTS 962,705 6/1910 Fielding ..72/453 PATENTEBMARZB 1972 3, 651 ,685

SHEET 1 OF 4 PATENTEDMAR28 m2 SHEET 2 [1F 4 PATENTEBMAR28 1972 ll l l l l PATENTEUMAR28 I972 3,651,685

sum u. [If a wmmm HIGH HYDRAULIC PRESSURE FORGING DEVICE The present invention relates to a forging machine wherein an impact pressure is applied to a part or entire surface of a blank of metallic material or other similar materials to thereby effect plastic deformation of said blank into a desired shape and configuration. More particularly, the invention relates to such forging machine and a die used in such machine wherein a high impact hydraulic pressure is utilized as a source of working force to forge and deform a workpiece.

The conventional methods for pressure molding of metallic material include hydraulic pressing, hydroforming and explosion molding processes. However, the hydraulic pressing or hydroforming process requires large-sized expensive pressure generating means, such as for instance high pressure pumps, with the resultant enhanced costs of equipment and complicated troublesome operations. Also, in the hydroforming process, the forming velocity is as slow as several to several mm. per second, and this poses a problem of possible water leakage during that time, so that additional means such as rubber membranes are required to provide protection against such leakage, with the result that the structure of the machine is still complicated and its service life appreciably reduced. A hammer or other similar devices are commonly and preferably used as the comparatively simple means for practicing such processes.

Conventionally known as the forging means are a steam hammer, a pneumatic power hammer and a drop hammer, wherein desired deformation is effected by application of an impact force. These devices, however, are actually required to have a fairly tough and strong frame and sufficient rigidity as a whole to stand sudden and heavy load which may be brought on from the nature of their uses. Also, since these devices utilize massive impact forces, they are mostly large-sized with heavy weight and hammer impact directly imparted to the die, so that when hammer speed is enhanced, possibility of damaging the die is accordingly enlarged, which may result in shortening the service life of the die. As long as kinetic energy of the hammer is used to effect direct forging, it is required for enhancing forging energy to increase either hammer speed or hammer weight. However, there is a certain limitation on hammer speed for the reason of durability, while an attempt of increasing hammer weight will inevitably result in enlarging the entire machine structure, thus adding to inconvenience and poor economy. In the case of a steam hammer, the die velocity is reduced with advancement of the momentary forging operations. In other words, the forging works are conducted with increasing loss of speed energy, so that it is not possible to optionally select the forging initiating velocity and, in addition, much waste of impact force is caused, which so greatly increases the risk of damaging the die, resulting in aggravating foreability and adversely affecting precision of the products.

Further, according to these devices, the forging operations are mostly carried out at a relatively large hammer stroke and at a velocity of 3 to 6 m./sec. As a simple and handy measure to obtain a strong forging power, attempts were made to employ a heavier hammer, but this only served to enlarge the machine structure, with forging efficiency remaining substantially unchanged. To meet an increasing demand for a highly efficient machine, a Dynapack and other high-energy forging machines, which permit high speed forging operations, were developed recently to take the place of the conventional inefficient devices. However, these machines, although producing a remarkably enlarged forging power by working at a high hammer speed of 20 to 40 m./sec. have also still proved disadvantageous in some points; for instance, these machines are more likely to invite damage or early wear of the forging die due to their too-high hammer speed, with consequent reduction of the die service life and undesirable effect to precision of the produced articles. Also, operating speed is inferior, if not largely to that of a steam hammer.

Generally, many types of dies are used for practicing the forging works. In case of hot die forging, the die is subject to the action of various and complicated forces resulting from, for instance, temperature rise caused by the hot material, friction caused by deformation resistance, or a massive impact force of the hammer. Particularly, at completion of the forging operation when the die is packed with the material, a large impact force of the hammeris apt to be converted through the workpiece into an outward tensile force acting directly to the die. Also, in hot forging die temperatu e rise is accompanied with reduction of tensile force which may become a cause of damage to the die, and also pressing force is not transmitted deep into the blank so that desired deformation is effected only on the surface, with resultant poor precision of the products.

Although it is a known fact that malleability of a metallic material is enhanced in a superhigh pressure atmosphere, there are frequent needs of forging an object with a shape very hard to form from material having high fluid resistivity. For example, the band of a wrist watch, or other small-sized articles similar to that, has to be forged so that its shape is beautifully formed, its round or angular corners neatly finished, and its dimensions highly exact. From the nature of its use, the chances are that the material is stainless steel having high resistance against forging. It has accordingly been very difficult to make forging only by striking in the vertical direction as it has been made by conventional forging machines of ordinary type. Moreover, in the case of effecting forging by holding material between the upper and lower dies, great tensile stress has been caused in corner portions of the die segments so that the die segments have had very poor durability due to the fissures caused by said tensile stress. Further, since direct striking force has not been applied from sideway directions, the shape in said directions has not been finished exactly, and the side portions of the forging have not been straight but slightly slanted due to the drawing slope adapted to facilitate the ejection of the forged substance from the dies, with resultant poor precision of the products. Due to the fact that material very hard to forge requires great energy to achieve desired forging work, there has been an inconvenience and economical disadvantage. As a result of application of the energy of great motion at a high striking velocity to a small die in the case of a small object, the die has either been easily flawed or retained only an extremely short service life.

It is, therefore, intended by the present invention to provide a forging device which permits most efficient and exact forging work by utilizing impulsive superhigh hydraulic pressure to give an extremely large force momentarily to material in the dies with use of a comparatively small-size apparatus to obtain large forging power.

The invention also aims at readily eliminating the defects inherent to the conventional devices by providing an arrangement in which the space between the fixed and movable dies used is kept comparatively narrow to diminish the die stroke and inhibit forging velocity from running too high, thereby keeping the die safe from breakdown.

It is another object of the invention to provide a forging machine having a construction which permits continuous repeated forging operations and remarkable reduction of the operating time and in which, if need be, the dies may be opened wide enough to facilitate extraction of the forged article, thus allowing easy forging operation at so much higher efficiency.

It is also an object of the present invention to provide a smalLsized and light-weighted forging machine which utilizes pneumatic force to produce extremely high striking hydraulic pressure which is applied to the material to be forged, thereby eliminating any risk of inviting fissures or other damages to the dies, and remarkably improve precision of the produced articles.

It is still another object of the present invention to provide a forging machine and a die assembly at low cost wherein no such tensile force, as is often present in the conventional forg ing dies, is produced to allow only a compression force to be afforded to the dies and whereby improved impact resistivity is given to the forging dies to keep them safe from incurrence of damage or trouble whatsoever.

Yet another object of the present invention is to provide a forging machine and a die assembly which eliminates the conventional defects to permit exact forging with enlarged energy even in the case of forging an article of a size and configuration which are hard to shape and which causes no tensile stress in the dies or the resultant fissure and also permits the material to be exactly shaped to every corner in confonnity to the mold.

It is also an object of the invention to provide means for facilitating extraction of the forged articles with no need of providing a slope in the dies and means for sufliciently intensifying forging energy without excessively enhancing the striking velocity to thereby achieve remarkably improved forgeability.

It is an additional object of the present invention to provide a forging machine in which, by making use of an inherent property of metallic material that its malleability is increased under an atmosphere of high pressure, a pressure medium of semi-solid (which is sufficiently fluid under superhigh pressure but normally a solid or an admixture of a solid and viscous fluid) is contained in a die cavity which has been sealed after combining a plurality of die segments, with a workpiece being placed therein, and superhigh pressure being instantaneously brought into said cavity to effect highly precise forging work under such atmosphere with case.

It is yet another object of the present invention to provide a forging machine and a die assembly which permit reduction of pressure liquid consumed in one forging operation, enable easy forging of a material with which it was hard to forge a small-sized article and produce uniform superhigh pressure on the entire surface of a material placed in the dies, to allow precise forging under compulsory lubrication of pressure medium by instantaneously flowing the material with timely application of impact force, thus making it possible to effect ideal forging work with large energy in cooperation with a means adapted to inhibit generation of tensile stress in the dies.

With these objects in view, the present invention discloses a forging machine wherein a hammer slidably mounted in a cylinder is accelerated and forcefully driven into liquid in a sealed liquid chamber to instantaneously generate impact hydraulic pressure. This pressure is given to a plunger forming a part of said sealed liquid chamber so that forging is effected between a die provided on said plunger and an opposed fixed or movable die.

An important feature of the present invention is that the forging machine is comprised of plural combined forging dies coupled to a ram housed in a cylinder at the back side thereof and arranged so that they are momentarily moved toward the center, or in the vertical or back and forth or right and left directions, by impact hydraulic pressure transmitted through a medium such as high pressure liquid from a high hydraulic pressure generating means.

Another important feature resides in a forging machine and dies thereof, wherein impact high pressure is produced in a medium such as liquid by an accelerated moving piston to effect forging by utilizing this produced high hydraulic pressure, characterized in that the forging dies are separated into upper and lower dies in the vertical direction and front, rear, right and left dies in the horizontal direction symmetrically, that there is provided a mechanism comprising an operating section whereby said impact hydraulic pressure is applied to the dies, an impact hydraulic pressure passage, a cylinder and a piston, and that forging actions are exerted to a workpiece simultaneously from all directions.

Still another feature of present invention is that plural combined dies are actuated by impact hydraulic pressure supplied from an impact hydraulic pressure generating means, that a workpiece and a pressure medium, such as an admixture of solid or solid powders and viscous fluid substance are placed in coexistence in the die cavity held by a large force in said dies, that impact pressure is introduced into said cavity to produce therein a superhigh pressure atmosphere, with such superhigh pressure being applied uniformly over the entire surface of the workpiece, and that the'workpiece is momentarily moved flowingly with application of impact force of one or more dies, thereby to effect desired forging and deformation under compulsorily reduced friction by pressure medium.

Still another feature of the present invention is that the forging machine is provided with means whereby, in case of practicing a forging work, the distance between a die on the movable side and a fixed or movable die opposed thereto is maintained small but sufficient to permit easy insertion of the workpiece thereinto and, in case of extracting the forged article, said distance between the dies is enlarged by a toggle mechanism or other means, that is, the invention is characterized by providing a subordinate mechanism which stops and retains the opposed dies at plural positions such as a position where the dies are sufficiently spaced from each other to facilitate the taking in and out of the forged articles, and a position where the movable die, immediately before application of striking force, is moved close to the workpiece but with a suitable space for giving such striking force most effectively.

Further, according to the present invention, by utilization of impact hydraulic pressure, an extremely large force is given to the dies by using a comparatively small-sized apparatus to obtain enormous forging power. Also, the distance between the dies in which the forging work is performed may be arranged comparatively small so that the movable die stroke is lessened, the forging forging velocity comparatively reduced and risks of causing damage to the dies eliminated. lt is also possible to conduct the repeated forging operations continuously with additional advantage of simplification of the forging process which can be performed in a short time.

Still further, the hammer impact is not directly exerted to the forging but is utilized to impingingly produce high hydraulic pressure which is applied to the plunger to obtain suitable forging velocity at which to effect desired forging operation at an optionally selected stroke. It is further possible, with this invention, to practice forging within a period of several milliseconds with high forging power, so that, even in case of hot forging, required working can be performed in a short time before the material is cooled, and also, in case of cool forging, high precision working can be made with large force.

Moreover, forging initiating velocity may be optionally selected by adjusting the distance between the dies before starting, which proves desirable for the reason of protection against possible damage to the dies as well as durability thereof, and in some cases, it is even possible to make substantially zero this forging initiating velocity and to apply static pressure, thus overcoming the difficulty of the dies likely to incur damage at high forging velocity, which is often observed in the conventional device, particularly in such devices where initial impinging velocity of the material against the dies is high and gradually lowered as seen in time shift of forging velocity of the conventional forging devices.

It should also be pointed out in this invention that the entire structure of the machine is simple and permits full and perfect utilization of applied superhigh hydraulic pressure. The machine may also be miniaturized with consequent reduction of weight as compared with the conventional hammers having the same striking capacity. The liquid pressure generating means and the forging operating means are composed integral, which adds to compactness of the machine and proves helpful to inhibit leakage of liquid pressure, thus permitting full utilization of liquid pressure; and since the operating hammer is adapted to compress liquid used as medium and accumulate energy therein, hammer speed may be strikingly increased unlike in the case where metal members are hit against each other, so that high forging energy may be obtained as working force with a small-sized and light-weighted hammer, resulting in improvement of acting force used for effecting forging deformation, remarkable enhancement of dimensional precision and elimination of any need of aftertreatments conventionally required for finishing work.

Still more, hammer energy is accumulated in the form of compression strain energy of liquid and causes rise of liquid pressure, whereby the forging section is accordingly accelerated to effect better forging operation, so that pertinent choice of the initial distance between the dies and material provides additional protection against damage to the dies, and at the same time permits maintenance of desired forging velocity, with resultant remarkable improvement of forgeability. in addition, means are provided whereby the distance between the opposed dies acting to the material to be forged is kept small sufficient only to permit quick and easy insertion of the material when so desired, said distance being sufficiently enlarged when it is desired to take out the forging, so that hammer speed need not be increased to any excess degree and therefore the dies are kept perfectly safe from breakage. The forging is not subjected to direct hammer impact but receives action of the forging practicing section through the medium of acting force produced by high hydraulic pressure, so that the mechanical troubles and inconveniences present in the conventional devices are completely removed to allow extremely efficient accomplishment of forging operations. Particularly, the hammer is struck into liquid to instantaneously and readily generate impact hydraulic pressure and this superhigh hydraulic pressure is transmitted to the operating members, such as plunger or ram, to perform forging between the movable and fixed dies, so that an increased forging power is obtained with a comparatively small-sized apparatus, thus providing additional advantage that the construction of the machine is assembled economically at surprisingly low cost.

The fissures likely to be inflicted during the forging process are caused by large impact force of the hammer acting as tensile force to the dies through the workpiece. However, according to the present invention, the dies undergo no tensile force but simply receive compression force as the only active force, which fact contributes greatly to enhancement of durability of the dies. Shaping of the forging die faces is usually made by a profiler, wherein it is found extremely difficult to give correct and exact shape to an elongated lobe or a tall and thin rib. The dies of the present invention, however, are assembled from separated die segments so that construction of the dies, even of an extremely complicated configuration, can be relatively easily realized by suitably shaping each die segment. It is also possible to synchronize the forging operation with the die shaping process by utilizing water or other liquids as a medium for transmission of energy from a high pressure source to the dies. Further, shaping may be achieved by moving the dies from periphery to center or from top to bottom and also positioning may be effected at the reference abutting face, so that the resultant forging is of uniform thickness and, in some cases, city water pressure may be used for effecting dismounting and releasing of the dies, thus providing additional significant improvement on the forging machine.

According to the present invention, the piston is accelerated by hydraulic pressure generated by energy transmitted instantaneously into the liquid from an impact hydraulic pressure generating means, and thereby impact forging of the material is conducted through the dies, so that it is possible to forge the material true to the dies under large hydraulic pressure and energy while keeping forging velocity sufficiently low to avoid damage to the dies. Further, the top and bottom dies may be fixed vertically, with other die segments being arranged movable horizontally so as to offer forging actions to the material from all directions. To realize this, liquid pressure may be utilized as active, medium, and also, such pressure may be exerted at as high speed as in a hydropunch, for instance, at a liquid pressure retaining time of 4/l,000 seconds, thus permitting simultaneous application of impact to the die assembly from all directions to provide extremely precise shaping to every corner of the article. Since each die segment can be pulled back at the time of removal of the product, there is no need of providing a drawing slope nor any fear of affecting precision of the product.

If the die assembly, arranged separatable vertically, rightwise and leftwise or back and forth, is incorporated in the apparatus of the present invention, no tensile force is produced in any of the separate die segments no matter what compression force is exerted thereto, so that the dies always remain safe from otherwise inevitable incurrence of fissures and can stand forging operations under sufficiently large force, whereby service life of the dies is even more elongated. If desired, the top and bottom dies may be composed integral to each other and the die segments may be arranged in separation along a plane where tensile force is considered to be acted, thereby to minimize concentration of tensile force in the dies. Attention is thus called to a surprising fact that although the conventional die devices could bear only several 10 rounds of forging operations, the apparatus of the present invention can stand as many as several hundred thousands of forging operations even if material of bad forgeability is used to shape a complicated configuration. Since the movable die segments receive synchronizingly balanced impact by hydraulic pressure from the same impact hydraulic pressure generating means, the forging process is conducted always at high precision and the obtained forging has no dimensional warps. Further, since the combined movable die segments are symmetrically opposed, the striking forces thereof work to cancel each other to make them substantially zero, thus completely eliminating incurrence of vibrations in the opposed direction.

The present invention also permits maximum utilization of the phenomenon that malleability of metallic material is increased under superhigh pressure atmosphere, and even in cool forging, it is possible to easily and properly provide the material with the same fluidity as in hot forging and also to produce compulsory friction reducing action by pressure medium to lessen fluid friction of the material, thus obtaining an excellent forged article beautifully shaped and having high dimensional precision.

The superhigh pressure medium flowing out from between the combined dies exerts its pressure to each die segment and produces a so-called Bridgmans anvil effect. Since pressure is extensively distributed on each face of each die segment, the die assembly is kept perfectly free from undesirable deformations which may be produced in case superhigh pressure is exerted only in one direction. Also, the dies may be constructed so as to be dividable vertically, right and left, or back and forth, and to receive no other acting force than compression force, so that even a material having bad forgeability and configuration may be easily forged, and also extension of service life of the dies as well as improvement in safety of operations and other economical advantages are realized.

in addition, energy transmitted instantaneously into liquid from the impact hydraulic pressure generating means is utilized as acting force for forging deformation and applied to the material in the dies to attain instantaneous shaping work, so that noises and vibrations resulting from application of impact forces are greatly reduced, thus eliminating any necessity of providing strong and rigid impact-resistive structure and permitting manufacture of the machines at low cost and with ease, with resultant remarkable reduction of forging cost as well as costs for equipment and other necessities.

In the present invention, superhigh pressure is instantaneously produced by utilizing impact force by an air punch or other means and this produced superhigh pressure is used as acting force in the forging operation, so that there is no need of providing a large-sized and costly pressure generating means such as is required in a hydraulic press or hydroforming process. Hence, remarkable reduction of costs for equipment and working operation is realized and also makes possible carrying on the processes successively by giving loads repetitively. Thus, forging operation for large dies can be performed by using a comparatively small-sized structure comprising an air punch, piston, plunger and the like. Also, impact force provided by a high-speed moving hammer is not transmitted directly to the metal members, but instead its impact energy is applied to the liquid to produce an impact hydraulic pressure (which amounts to several thousand atmospheric pressures) to thereby effect instantaneous shaping, thereby making it possible to obtain a structure having suprisingly improved durability without any need of paying annoying considerations to protection of otherwise possible leakage of liquid, the obtained structure being able to stand several hundred thousands of rounds of forging works.

In the following, there will be discussed some preferred embodiments of the present invention, but it is to be understood that the invention is not limited to the particular embodiments, but various other means effective for obtaining the same or even better forging workability, improvements of product precision, and also, enhancement of durability of the composing elements may be suitably applied and adapted in the structure.

The accompanying drawings show a few of the embodiments of the present invention, in which:

FIG. 1 is a sectional side view of an apparatus according to the present invention;

FIGS. 2 to 12 show other embodiments not deviating from the scope of the present invention, with FIG. 2 showing a side view illustrating another embodiment ofa positioning member ofa movable die;

FIG. 3 is a sectional side elevation showing another embodiment of a mechanism including the principal parts of a high hydraulic pressure generating assembly;

FIG. 4 and 5 are side views of still other embodiments of the present invention, with a part cut away to show operative conditions of the composing elements;

FIG. 6 is an enlarged longitudinal sectional view of a part of the structure shown in FIG. 4;

FIG. 7 is a partly cut away plane view of another embodiment of the die used in the apparatus ofthe present invention;

FIG. 8 is a sectional side view as taken along the line 11 of FIG. 7;

FIGS. 9 to 11 show still another embodiment, in which FIG. 9 is a longitudinal sectional view of the die assembly;

FIG. 10 is a sectional plane view as taken along the line 1111ofFIG.9;

FIG. 11 is a sectional plane view of another embodiment as taken in the same manner as in FIG. 10; and

FIG. 12 is a longitudinal sectional view of the die cavity section in the structure shown in FIG. 11.

The invention will now be described in more detail about each element with reference to the drawings.

First, referring to FIGS. 1 to 6, a sealed pressure-proof vessel 1 in which water or other liquid is to be filled has provided therein a cylinder 2 which in turn has slidably mounted therein a working member comprising a hammer 3 and a plunger 4, which may be formed integrally or may be provided separately, and a means for driving said working member at high speed whereby high speed impact force is given to the plunger 4 from outside of the cylinder 2 or negative pressure of air or compression air is introduced through an air duct 5 at the top of the cylinder 2 to thereby cause vertical movements of the working member. The vessel 1 has also formed therein a hydraulic pressure chamber 6 which is communicated with a guide hole 7 of said working member to provide an impact hydraulic pressure generating means wherein when the working member is plunged into the hydraulic pressure chamber 6, liquid in said chamber is compressed to instantaneously produce a high impact hydraulic pressure with which to effect desired shaping ofa metallic material. As will also be noted, a ram hole 8 is communicated with the hydraulic pressure chamber 6, and in said ram hole 8 is movably mounted a ram 9 to which a die pedestal 10 is directly attached, and a die 11 is secured to said die pedestal 10 so that said die is movable. Opposed to said die 11 is provided a corresponding fixed or movable die 12 mounted on a base block 14, said base block 14 and pedestal 10 being connected together through supports 13, thereby constituting a forging operating assembly.

Said ram hole 8 and ram 9 may be formed as a plunger guide and a plunger, respectively, and the selection may be made optionally to meet the situation, provided that they are arranged slidable with respect to each other. The ram 9 may also be mounted directly to the die 11 without medium of the pedestal 10, in which case the die 11 should preferably be arranged demountable. The die pedestal 10 is also provided with a positioning mechanism 15 for vertical movements of the ram 9, whereby clearance between both dies may be conveniently adjusted. This positioning mechanism 15 may be preferably composed either of an assembly comprising a hydraulic cylinder 16, a piston 17 and an oil feeding-and-discharging valve 18, as shown in FIG. 1, or of a toggle mechanism wherein a piston is slidingly moved along a guide 19 and pivoted at a fulcrum 22 through a bent link 20 and a return spring 21 as shown in FIG. 2, whereby the distance between the dies 11 and 12 is varied by suitably moving the pedestal 10 to place movable dies therein. Said moving die pedestal 10 may preferably be arranged to move while being guided by supports such as stanchions 13, for assuring precision of the produced articles. Said hydraulic pressure chamber 6 is filled with water, glycerin or other liquids as medium. Although it is structurally convenient to communicate said chamber with the guide hole 7 through a hydraulic pressure passage 23, arrangement may also be made such as shown in FIG. 3 where the hydraulic pressure chamber 6 doubles as the ram hole 8.

In the arrangement shown in FIG. 3, the plunger 4 is accelerated downwardly and moves in the cylinder 2 to produce impact. The supporting block 14 having mounted thereon the die segment 12 is provided with a piston 24 which is movably fitted in a compressed air cylinder 26 communicated with a compressed air chamber 25 so that the block 14 is pushed up to a certain level from below by the compressed air to keep the distance between both die segments 11, 12 as desired. In this case, the moving passage of the plunger 4 is opened to the atmosphere through a vent 27 to inhibit generation ofnegative pressure resistance and to permit efficient sliding motion of the hammer 3 in the cylinder 2. The die supporting block 10 is normally retained at the position shown in the drawing by a nocking means (not shown) but is released from the nock at the moment of application of impact. It is again locked by availing of ascending movement of the block 14. When it is desired to take out the forged material, the compressed air in the compressed air chamber 25 is let out to enlarge the space between the die segments.

The die base block 14 should preferably be of large mass quantity and sufficiently heavier than the moving die pedestal 10. It will for instance be reasonable to select the mass quantity so that when, for example, the forging operation is conducted at a pedestal velocity of say 20 m./sec., kinetic energy is absorbed up by the material to permit smooth forging operation, with the block 14 being ultimately moved only slightly downward.

Therefore, in a condition such as shown in FIGS. 1 and 3, if a material to be forged is placed between the dies 11, 12, with suitable spaces being maintained therebetween, and then the impact hydraulic pressure generating assembly is actuated to urge the plunger 4 at the bottom end of the hammer 3 to rush into the liquid in the hydraulic pressure chamber 6 at high speed, the liquid is momentarily compressed to impulsively produce a superhigh pressure of, for example, 4,000 or more atmospheric pressures (it is even possible to produce as high as 10,000 atmospheric pressures). This hydraulic pressure is instantaneously transmitted through the hydraulic pressure chamber 23 or directly to the liquid in the chamber 6, and the ram 9, on receiving such high water pressure, works to forcefully bring the die pedestal 10 and the die 11 thereon into the ram hole 8 so that the material to be forged is securely held between said movable die 11 and its counterpart 12 on the base block 14, thus permitting ensuing positive and correct forging operation. On completion of this round of forging operation, the die block 10 is restored to its original position owing to its own weight or by an acting force applied thereto to stay ready for the next round of operation. Such forging operation may be conducted repeatedly as many times as desired. With completion of the forging operation, the die block 10 is guided by the working mechanism 15 to the limit of its stroke, whereby the space between the dies l1, 12 is widened enough to facilitate removal of the shaped article. The total amount of force acted to the ram 9 is a sum of multiplication of hydraulic pressure provided from the impact hydraulic pressure generating assembly by the sectional area of the ram 9, so that it is possible to select any desired forging initiating velocity by properly regulating the time shift of forging capacity and forging velocity to produce the most effective performance substantially at the moment of initiation of forging operation and by also suitably adjusting the initial clearance between the dies 1 l, 12. This fact does much to provide high reliability for protection against any possible damage to the dies as well as for the attainment of best forging practice.

The embodiment shown in FIGS. 4 to 6 has the same impact hydraulic pressure generating mechanism (in which, however, the hydraulic pressure chamber 6, plunger 7 and ram hole 8 are formed in a common space), but particular consideration is paid to the mechanism of the moving die block 10; namely, in this embodiment, plural guide rods 28 are provided in the block 10 in such a manner as to extend downward from said block and pass through holes 29 of the base block 14 to be vertically movable by pneumatic force or by other means. Said rods are also so arranged that they may be optionally moved upwards or downwards by a portion (not shown) connected thereto and may be stopped at a predetermined position by a stop device. The construction of this section, as best shown in FIG. 6, is arranged in such manner that a piston 33 is located in an air cylinder 32 having formed therein a compressed air inlet 30 and outlet 31, with said guide rod 28 being coupled to said piston 33 so as to be vertically moved by compressed air force. Said piston 33 is also provided with a rod 34 having a nock 36 mounted to be able to jet out and draw back through a spring 35. Said nock 36 is inserted into a notch 38 formed in a fixing block 37 to stop the assembly. There are two stopping positions. One is a position where the movable die 11 is raised up sufficiently to provide enough space to permit easy taking in and out of the material between the movable die ll 1 and the fixed die 12 (see FIG. 4), and the other is a position where the movable die 12 is approached close to the material immediately before application of forging impact force; that is, in this position said die stays close to the material but with a sufficient space to allow most effective application of the striking force.

The air duct at the top of the cylinder 2 is connected to an outside compressed air source through an electromagnetic valve (not shown) to serve either as a passage for introducing the compressed air or as a passage for letting out the air by a vacuum pump or other means. It will also be noted that the hammer 3 has integrally formed at its bottom a plunger 4 adapted to produced impact hydraulic pressure. An opening 27 formed in the cylinder 1 serves to connect the interior of the cylinder 2 below the hammer 3 with the atmospheric air during upward or downward stroke of the hammer 3 to keep the cylinder 2 interior substantially at the atmospheric pressure. The hydraulic pressure chamber 6 has communicated thereto a water conduit 39 which is connected through a valve (not shown) to a water main or other water source to feed water from outside by automatically or manually opening the valve. In case of using liquid other than water, such as glycerine or the like, in the liquid pressure chamber 6, appropriate measures should be taken to cope with compression or lubricating characteristics of the particular liquid or its corrosiveness to the metallic parts.

FIG. 5 shows another operative condition where the hammer 3 was dropped by compressed air force to oppress the movable die 1 1 directly connected to the die block so as to press and forge a material placed between said die 11 and the fixed die 12. As the preliminary operations that precede said forging operation, first the hammer 3 in the cylinder 2 is raised up to the top end of the cylinder 2 by negative pressure exerted to the air duct 5 while the die block 10 is lifted up by the guide rods 28 (FIG. 4), and in this position a material to be Iii forged is placed on the fixed die 12, and then the die block 10 is moved down with movement of the guide rods 28 to a suitable position close to the material on the fixed die 12. Water is then fed through the water conduit 39 to fill the hydraulic pressure chamber 6 and the ram hole 8. When feeding is sufficient to overflow from the opening 27, the valve is closed to stop feeding of water through the conduit 39.

Negative pressure from the air duct 5 is then changed over to introduce compressed air into the air duct 5, whereby the hammer 3 is accelerated by the air duct force and falls in the cylinder at high speed, causing the plunger 4 to dash violently into the plunger hole 7 to thereby compress water in the hydraulic pressure chamber 6 and impulsively produce high pressure. This impact water pressure causes the ram 9 in the ram hole 8 to be instantaneously accelerated and moved downward so that the die 11 mounted on the die block 10 directly coupled to the ram 9 hits and forges the material on the fixed die 12 (FIG. 5). On completing this the die block 10 is again raised up by said guide rods 28 to take out the forged material, during which period the vessel l and the cylinder 2 still remain connected to the base block 14 by the supports 13. It is thus possible to produce extremely high pressure impulsively by using air force. For instance, water pressure of several thousand atmospheric pressures can be produced in a very short time with compressed air of from 5 to 20 atmospheric pressures, whereby large impact force of several hundred to several thousand tons is generated to perform positively and efficiently the desired high speed forging operations.

It should also be noted that the hydraulic pressure chamber 6 or the guide hole 7 into which the hammer 3 or the plunger 4 is driven is so arranged that its inlet wall 49 is cut in the form of a funnel or a cup to form a bevel or curved face as shown in FIGS. 3 to 5, while the dashing face of the hammer 3 or the plunger 4 is formed convexly, so that when the hammer 3 or the plunger 4 approaches the liquid face at high speed, the liquid face moves on receiving compressive force thereof but remains safe from being disturbed by such force thanks to the said configuration of the dashing face of the hammer or plunger. The above arrangement eliminates any fear of inviting bubbling or swelling of liquid surface which may cause intrusion of foams into liquid, requiring a troublesome step of compressing such foams at the time of the rise of liquid pressure.

An air punch may be used instead of air pressure, as shown in the drawing, as a means for giving impact to the hammer 3 or the plunger 4 from outside. The hydraulic pressure chamber may be composed integral with said air punch in which the plunger itself is formed as a part of the air punch. The construction of the hydraulic pressure chamber 6 may also be so arranged that the communicated flow passage area is sufficiently reduced to make it possible to obtain desired high pressure and'that thickness of the outside wall of the passage is gradually increased to form another rational hydraulic pressure chamber structure.

Now referring to FIGS. 7 to 12, there is shown another embodiment which has the same impact hydraulic pressure generating assembly as described above and in which produced superhigh pressure is transmitted through water or other medium to provide impact hydraulic pressure which causes the movably arranged dies to instantaneously move toward the center, or from top to bottom, or back and forth, or right and left, or in combination, to thereby practice a forging work. In this embodiment, a specific characteristic feature is incorporated in its die mechanism.

In the embodiment shown in FIGS. 7 and 8, the die 42 has provided at its backside a cylinder 40 communicated through a hydraulic pressure passage to the impact hydraulic pressure generating means and a ram 41 slidably mounted in said cylinder 40. There are provided such dies in plurality which are combined to form the external die assembly. A movable middle die 44 communicated with said impact hydraulic pressure generating means such as a hydropunch is arranged to be thrustable from above or from below into a sealed cavity 43 sealingly surrounded by said external dies. Said cylinder 40 is filled with liquid such as water or oil, and the middle die 44 is communicated with the high hydraulic pressure generating means through a punch means 45 which doubles as a plunger. A base block 46 supporting the combined external die assembly has a slot 47 in which the middle die 44 is fitted. A chamber 48 on the opposite side is connected to a valve whereby change-over to the atmospheric air or to hydrostatic pressure, for example, water main, is effected.

Under this arrangement, a material (a ring-shaped material is most effective in this case) is placed in the sealed cavity 43 and then the impact hydraulic pressure generating means is actuated. Generated energy is instantaneously transmitted into the cylinder 40, causing the dies 42 coupled to the ram 41 to move toward the center, and in conformity with this movement, the middle die 44 is also accordingly moved downward at a fairly high speed, thereby performing forging of the material. If the cylinder 40 is opened and the chamber 48 on the opposite side is manually or automatically switched to hydrostatic pressure, each of the combined dies is forced by liquid to return to its original position to get ready for the next operation.

In this manner each of the separate dies receives no tensile force but is simply applied with compressive force as acting force, so that durability of the dies is remarkably improved, and also since liquid is utilized as a medium for transmission of energy from a high pressure source to the dies, it is easy to synchronize the shaping process and timing.

Shown in FIGS. 9 and is still another embodiment which also uses the separate dies to perform forging. In this embodiment a die frame 50 is provided fixedly on the base block 14, said frame 50 having formed therein a guide hole 51 in which a bottom die body 52 is vertically slidably fitted. On top of said bottom die body 52 is mounted a bottom die 53, and at the bottom thereof is provided a ram 54 having a bevel formed at the bottom face thereof. Said ram 54 is slidably fitted in a ram hole 55 formed in the die frame 50 and is interlocked with an operating rod 56 which is actuated from outside through an air cylinder or hydraulic cylinder (not shown). Said bottom die body 52 should preferably be made of steel having high rigidity and be as heavy as the situation permits so as to provide large inertia resistance sufficient to cope with high impact experienced during the forging operation.

Usually plural wedges 57 slidably interposed between said base block 14 and the ram 54. An operating rod 58, which is actuated from outside by an operating means such as an air or hydraulic cylinder, is coupled at its threaded portion 59 to each of said wedges 57. Said wedges 57 are pressed into the underside of the ram 54 or pulled out therefrom to help make positioning adjustment. In another guide hole 61 (usually rectangular in section) of said die frame 50 is slidably mounted an upper die 50 which has formed at its bottom face a convexity or concavity corresponding to the shape to be forged, and thereunder is formed a die cavity 62 in which a material to be forged is inserted. The upper die 60 is coupled with a threaded portion 64 of an operating rod 63 which is actuated from outside by an operating source such as an air or hydraulic cylinder to vertically move the die 66. In this case, the threaded engagement of the portion 64 of the operating rod 63 with the die 60 should preferably stay loose, since by so doing, the impact force afforded to the die will not be directly conveyed to the operating rod 63 so that said rod remains safe from damage that can otherwise result from such impact. The upper die 60 is usually of non-circular shape, such as, for example, a rectangle and is movably fitted in the guide hole 61 so that the die 60 will not be incorrectly directed or shifted, or otherwise varied in an undesirable manner during forging. Abutted to this upper die 60 is a piston 65 which is slidably disposed in a cylinder 66 atop the die frame 50.

The operating rod 63 coupled to said upper die 60 passes through a central through-hole 73 of the piston 65 and extends outside to be connected to a power source. Said piston 65 is formed with a cylindrical flange 67 which is fitted in the hydraulic pressure chamber 68 of the cylinder 66 to divide said chamber into an upper liquid compartment 69 and a lower space 70. The upper compartment 69 is communicated through a hydraulic pressure passage 71 to an impact hydraulic pressure generating means such as a hydropunch and filled with liquid. The lower space 70 vents to the atmospheric air through an opening 72 to prevent generation of negative pressure resistance. In this case, should liquid in the upper compartment 69 leak from a void between the piston flange 67 and the cylinder 66 and flow into the lower space 72, said opening 72 serves as a flow passage for discharging such leaking liquid outside of the machine.

There are also provided side dies having the same construction as the components of the upper die 60, said side dies being arranged in plurality around the die cavity 62 and combined with each other to form a side die assembly. In the embodiment shown in FIGS. 9 to 11, four such side dies 80 are provided at four sides, front, rear, right and left, of the die frame 50. Therefore, impact is given vertically from said upper die 60 and simultaneously crosswise from said separate side dies 80, thus remarkably improving forgeability of the workpiece. The construction and operation of said side dies 80 are completely identical with those of the upper die 60 so that there will be no need of describing them here. The hydraulic pressure passage 91 of each side die 80 is of the same arrangement as the hydraulic pressure passage 71 of the upper die. It is communicated to the same impact hydraulic pressure generating means and is arranged to be given the same hydraulic pressure at the same timing.

The embodiment shown in these figures is illustrated on the assumption that said embodiment is utilized for forging the band of a wrist watch but forging machines for a simpler object may do only with an upper die 60 and a lower die 53, or the side dies 80, 80 in front and rear directions or those in left and right directions. For a special purpose, the dies, instead of being composed crosswise, may be composed so as to face the center of the die cavity 62 from three, five or more corners so that forging in the shape of a trigonal or polygonal prism may be effected. Thus the composition of components such as a combination of the die frame 50 and the side dies 80 can be determined in accordance with the shape and structure of an object to be forged, but care should be taken so that the components are arranged symmetrically to balance the striking powers in the horizontal directions. Of course, the upper die 60, lower die 53 and side dies 80 enclosing the die cavity 62 are all formed with concave or convex faces corresponding to the shape of the article.

In the drawings, 74, 77 denote sealing means such as 0- rings provided in the cylinders, 76, 78 piercing holes for receiving the operating rods therein, 81 guide holes for the side dies, 84 threaded portions of said operating rods, 85 pistons, 86 cylinders for the side dies, 87 cylindrical flanges, 88 hydraulic pressure chambers, 89 liquid chambers, 90 spaces, 92 air and liquid exhaust ports and 93 through-holes.

The bottom die body 52 inside the guide hole 51 in the die frame 50 fixed on the base block 14 is lowered due to its own weight, to be stopped as the ram 54 at the foot portion thereof contacts the base block 14. In this instance, the operating rods 58 are contracted downward and the wedges 57 are drawn by the operating rods 58 to a point wherein said wedges come off the lowest side of the ram 54. The upper die 60 and the front, rear, right and left side dies 80 are completely drawn by the operating rods 63, 83 up to a point where the hydraulic pressure chambers 68, 88 and the liquid chambers 69, 89 are excluded. Thus the die cavity 62 is opened wide enough to insert the forging material onto the lower die 53 through an opening adequately provided in the die frame 50.

Next, the bottom die body 52 is pushed up with the operating rod 56 and at the same time the wedges 57 are advanced by the operating rods 58 to facilitate pushing up to the bottom die body 52. (In this case, suitable stoppage should preferably be provided in the base block 14 so that the wedges 57 are stopped at a predetermined position.) By lowering said operating rod 56 in this instance the bottom die body 52 is mounted on the wedges 57. Thereafter, the operating rods 63, 83 are moved from the outside so as to advance the upper die 60 and the side dies 80 in front, rear, right and left positions until they come to lightly touch the material to be forged or approach close to said material, and simultaneously, by supplying water to the hydraulic pressure passages 71, 91, from a source such as a hydrant, pistons 65, 85 will be advanced until they are stopped by contacting the upper die 60 and the side dies 80.

In this instance, by applying the hydraulic pressure generated in an impact hydraulic pressure generating means, such as a hydropunch to the liquid chambers 69, 89 simultaneously through the hydraulic pressure passages 71, 91, the pistons 65, 85 are accelerated by the impact hydraulic pressure and simultaneously hit said upper die 60 and side dies 80 so that the top and side faces of the workpiece in the cavity 62 are forged in conformity to the shape of the dies 60, 80.

The lowest surface of the workpiece is also forged in accordance with the shape of the bottom die 53 since the material is placed on the bottom die 53. During this operation, the bottom die 53 is not moved by the striking impact, as said die forms an integral unit together with the bottom die body 52 having a great weight so that the bottom die is possessed of great inertia resistance against impact strikes and the ram 541 at the bottom thereof is rigidly supported by the wedges 57 on the base block 14. Also, since each of said side dies 80 strikes the workpiece simultaneously with hitting against said material by the upper die 60, the workpiece flows instantaneously at the moment of said impact strikes and is forged in conformity with the shape of the die cavity 62 formed by the dies. The striking powers of the side dies 80 are aimed at opposite directions so that, while and after forging of the workpiece, their acting forces are counterbalanced relative to each other and thus cause no vibration outside in the horizontal direction. Upon completion of forging, the dies 53, 60, 80 are retreated by the operation rods 56, 63, 83 in a sequence opposite to the foregoing and the whole operational procedure is terminated with the ejection ofa forged product.

Thus, the pistons are accelerated by energy in the form of a hydraulic pressure transmitted impulsively into the liquid by the impact hydraulic pressure generating means whereby the workpiece is struck and forged by the dies, so that the workpiece can be forged in accordance with a required shape with high hydraulic pressure and energy while the striking speed is kept in such a low degree as not to cause flaw in the dies.

The embodiment shown in FIGS. 11 and 12 is composed of substantially the same structural arrangement as in the embodiment exemplified in FIGS. 9 and 10. However, in the instant embodiment, the front, rear, right and left hydraulic pressure chambers are not designed to provide striking impact but to serve as means for retaining a composed die cavity. There is also provided a plunger member 79 adapted to produce superhigh pressure in the die cavity 62 formed by combination of the bottom die 53, upper die 60 and side dies 80. Every acting face of each of said dies 53, 60, 80 is worked into a concavity or convexity corresponding to the shape of each face of an article to be forged, and the plunger member 79 for producing superhigh pressure in the die cavity 62 is pro vided in continuation to such concave or convex faces. Provided in communication with said plunger member is an exhaust port 75 of pressure medium which flows out with advancement of superhigh pressurization and shaping of the material, said exhaust port being located around the guide hole 61 in the die frame 2 and fronting the side dies 80.

The space in the die cavity 62 is opened sufficiently wide in the same manner as in FIG. 9, and a material surrounded by pressure medium of semi-solid is inserted through a hole in the die frame 50 and placed on the lower die 53. As pressure medium, a substance which has sufficient fluidity under superhigh pressure but is normally solid powders or an admixture of solid and viscous fluid, for example a mixture of grease and graphite or talc, is coated around the material.

Thus, when hydraulic pressure, issued from the impact hydraulic pressure generating means is exerted simultaneously to the liquid chambers 69, 89 through the hydraulic pressure passages 71, 91, the upper die 60 accelerated by impulsive high hydraulic pressure is thrust into the die cavity 62 composed of the bottom die 53 and the front, rear, right and left side dies whose combined setup is securely held by large force through the front, rear, right and left pistons 85, whereby the pressure medium surrounding the material instantaneously flows and fills the die cavity 62. A part thereof flows out to the discharge port 75, but the remainder is throttle at the plunger section 79 to cause rapid rise of pressure in the cavity 62, resulting in increasing fluidity of the pressure medium. The material is caused to flow instantaneously at the same time with the impact strike of the upper die 60 while receiving said superhigh pressure uniformly over its whole surface, and die forging is effected under the aid of antifrictionality of the pressure medium to obtain an article forged into the shape of the die chamber 62 composed of said dies 53, 60, 80.

In this instance again, each of the side dies 80 receives large back pressure sufficient to cope with superhigh pressure in the dies so that the dies are not retained. Also, the acting forces of the dies in the opposed directions are counterbalanced with respect to each other so that no vibration is caused outside in the horizontal direction.

Thus, in this embodiment, a workpiece surrounded by a pressure medium of, for example, semi-solid is placed in a die chamber composed of a plurality of separate dies combined together and whose composition is retained with large force, and superhigh pressure is caused in the die cavity 62 by means of a plunger doubling as an upper die driven by impact hydraulic pressure, and simultaneously forging effected in this atmosphere, the workpiece presents as good fluidity in a cold atmosphere as in the case of hot forging due to the increase of malleability of the metallic material under superhigh pressure. Also forged products whose surfaces are beautifully finished and which have high exactitude in dimensions are obtained due to the compulsory antifrictional operation of the pressure medium against the flow resistance of the material. Further, although each segment of the separated dies is subject to compressive power, they are so composed that no tensile force is applied thereto, so that cracks are not caused in the dies, which therefore permits forging with even greater power. it is thus possible to easily attain high precision forging work even from a material having large forging resistance such as stainless steel.

Furthermore, since the movable dies are subjected to simultaneous striking impact by hydraulic pressure from the same impact hydraulic pressure generating means, even in forging of material having bad forgeability, the device of the present invention can stand several hundred thousands of forging strikes. Thus the present invention presents enormous contribution to the forging industries.

I claim:

1. A high pressure forging apparatus comprising a body portion having a chamber therein for receiving liquid to a predetermined level; hammer means, said chamber defining a cylinder for the slidable displacement of said hammer means from an initial position above said predetermined level of said liquid; said body portion being formed with bores therein defining at least two further cylinders and providing communication between said further cylinders and said chamber below said predetermined level of said liquid; a plunger means received within each of said further cylinders for slidable displacement therealong, both said plunger means being in operative engagement with said liquid; and die means incorporating at least two spaced dies movable toward and away from each other, one of said movable dies each being secured to each one of said plunger means, said hammer means being adapted for accelerative displacement toward said liquid for the production of impact hydraulic pressure in said chamber when said hammer means is driven into said liquid, which pressure is in turn applied as operating force to said plungers for the coordinate and simultaneous displacement of said movable dies toward each other.

2. A high hydraulic pressure forging apparatus as recited in claim 1, wherein said die means incorporates a central workpiece receiving region and a plurality of dies symmetrically disposed about said workpiece receiving region and movable toward and away therefrom; a plurality of said plunger means, one of said movable dies being secured to each of said plunger means; and a plurality of said further cylinders communicating to said chamber below said predetermined liquid level, one of said plunger means being slidably movable in each of said further cylinders for the coordinate and simultaneous displacement of said movable dies toward said workpiece receiving region in response to said impact hydraulic pressure in said liquid, whereby tensile force produced in said dies is minimized.

3. A high hydraulic pressure forging apparatus as recited in claim 2, wherein said plurality of movable dies are substantially positioned in a plane so that the respective paths of displacement of said movable dies extend in a radial direction from said work piece receiving region; said apparatus including a further die movable toward and away from said workpiece receiving region along a path extending substantially normally to said plane; a further plunger means secured to said further die; and a further cylinder communicating to said chamber below said predetermined liquid level and having said further plunger slideably movable therein, whereby said plurality of movable dies and said further die are coordinately and simultaneously displaced toward said workpiece receiving region in response to said impact hydraulic pressure in said liquid.

4. A high hydraulic pressure forging apparatus as recited in claim 3, including a fixed die in opposition to said further movable die, said fixed die being adapted to have large inertia resistance against the impulsive striking force of said movable dies.

5. A high hydraulic pressure forging apparatus as recited in claim 3, wherein a viscous fluid presenting fluidity under superhigh pressure is received in said workpiece receiving region, along with said workpiece, whereby the high pressure is applied uniformly over the entire surface of said workpiece, said pressure medium serving to reduce the friction of the forging operation.

6. A high hydraulic pressure forging apparatus as recited in claim 3, wherein an admixture of grains presenting fluidity under superhigh pressure is received in said workpiece receiving region, along with said workpiece, whereby the high pressure is applied uniformly over the entire surface of said workpiece, said pressure medium serving to reduce the friction of the foregoing operation. 

1. A high pressure forging apparatus comprising a body portion having a chamber therein for receiving liquid to a predetermined level; hammer means, said chamber defining a cylinder for the slidable displacement of said hammer means from an initial position above said predetermined level of said liquid; said body portion being formed with bores therein defining at least two further cylinders and providing communication between said further cylinders and said chamber below said predetermined level of said liquid; a plunger means received within each of said further cylinders for slidable displacement therealong, both said plunger means being in operative engagement with said liquid; and die means incorporating at least two spaced dies movable toward and away from each other, one of said movable dies each being secured to each one of said plunger means, said hammer means being adapted for accelerative displacement toward said liquid for the production of impact hydraulic pressure in said chamber when said hammer means is driven into said liquid, which pressure is in turn applied as operating force to said plungers for the coordinate and simultaneous displacement of said movable dies toward each other.
 2. A high hydraulic pressure forging apparatus as recited in claim 1, wherein said die means incorporates a central workpiece receiving region and a plurality of dies symmetrically disposed about said workpiece receiving region and movable toward and away therefrom; a plurality of said plunger means, one of said movable dies being secured to each of said plunger means; and a plurality of said further cylinders communicating to said chamber below said predetermined liquid level, one of said plunger means being slidably movable in each of said further cylinders for the coordinate and simultaneous displacement of said movable dies toward said workpiece receiving region in response to said impact hydraulic pressure in said liquid, whereby tensile force produced in said dies is minimized.
 3. A high hydraulic pressure forging apparatus as recited in claim 2, wherein said plurality of movable dies are substantially positioned in a plane so that the respective paths of displacement of said movable dies extend in a radial direction from said work piece receiving region; said apparatus including a further die movable toward and away from said workpiece receiving region along a path extending substantially normally to said plane; a further plunger means secured to said further die; and a further cylinder communicating to said chamber below said predetermined liquid level and having said further plunger slideably movable therein, whereby said plurality of movable dies and said further die are coordinately and simultaneously displaced toward said workpiece receiving region in response to said impact hydraulic pressure in said liquid.
 4. A high hydraulic pressure forging apparatus as recited in claim 3, including a fixed die in opposition to said further movable die, said fixed die being adapted to have large inertia resistance against the impulsive striking force of said movable dies.
 5. A high hydraulic pressure forging apparatus as recited in claim 3, wherein a viscous fluid presenting fluidity under superhigh pressure is received in said workpiece receiving region, along with said workpiece, whereby the high pressure is applied uniformly over the entire surface of said workpiece, said pressure medium serving to reduce the friction of the forging operation.
 6. A high hydraulic pressure forging apparatus as recited in claim 3, wherein an admixture of grains presenting fluidity under superhigh pressure is received in said workpiece receiving region, along with said workpiece, whereby the high pressure is applied uniformly over the entire surface of said workpiece, said pressure medium serving to reduce the friction of the foregoing operation. 